Abstract

Background

When mismatches in heteroduplex DNA formed during meiotic recombination are left unrepaired,
post-meiotic segregation of the two mismatched alleles occurs during the ensuing round
of mitosis. This gives rise to somatic mosaicism in multicellular organisms and leads
to unexpected allelic combinations among progeny. Despite its implications for inheritance,
post-meiotic segregation has been studied at only a few loci.

Results

By genotyping tens of thousands of genetic markers in yeast segregants and their clonal
progeny, we analyzed post-meiotic segregation at a genome-wide scale. We show that
post-meiotic segregation occurs in close to 10% of recombination events. Although
the overall number of markers affected in a single meiosis is small, the rate of post-meiotic
segregation is more than five orders of magnitude larger than the base substitution
mutation rate. Post-meiotic segregation took place with equal relative frequency in
crossovers and non-crossovers, and usually at the edges of gene conversion tracts.
Furthermore, post-meiotic segregation tended to occur in markers that are isolated
from other heterozygosities and preferentially at polymorphism types that are relatively
uncommon in the yeast species.

Conclusions

Overall, our survey reveals the genome-wide characteristics of post-meiotic segregation.
The results show that post-meiotic segregation is widespread in meiotic recombination
and could be a significant determinant of allelic inheritance and allele frequencies
at the population level.